de Havilland DHC-6 Twin Otter

Airworthiness Directives; Viking Air Limited (Type Certificate Previously Held by Bombardier, Inc. and de Havilland, Inc.) Airplanes

The FAA is adopting a new airworthiness directive (AD) for certain Viking Air Limited (type certificate previously held by Bombardier Inc. and de Havilland, Inc.) Model DHC-6-1, DHC-6-100, DHC- 6-200, DHC-6-300, and DHC-6-400 airplanes. This AD was prompted by mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI identifies the unsafe condition as binding of the rod end bearing connecting the lower fuel control unit (FCU) push rod assembly to the FCU power lever. This AD requires performing tests, inspections, and lubrication of the FCU push rod assemblies, and replacing them with improved parts as necessary. The FAA is issuing this AD to address the unsafe condition on these products.

Airworthiness Directives; Viking Air Limited (Type Certificate Previously Held by Bombardier Inc. and de Havilland, Inc.) Airplanes

The FAA is adopting a new airworthiness directive (AD) for all Viking Air Limited (Viking) (type certificate previously held by Bombardier Inc. and de Havilland, Inc.) Model DHC-6-1, DHC-6-100, DHC- 6-200, DHC-6-300, and DHC-6-400 airplanes. This AD results from mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI identifies the unsafe condition as cracks and corrosion damage to the aileron internal structure. This AD requires visually inspecting the entire aileron internal structure, correcting any damage found, and reporting the inspection results to Viking. The FAA is issuing this AD to address the unsafe condition on these products.

Airworthiness Directives; Viking Air Limited (Type Certificate Previously Held by Bombardier, Inc. and de Havilland, Inc.) Airplanes

The FAA is superseding Airworthiness Directive (AD) 89-24-06 R1, which applied to all Boeing of Canada, Ltd. and de Havilland (now Viking Air Limited) Model DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-300 airplanes. AD 89-24-06 R1 required repetitively inspecting the elevator quadrant for damage and taking corrective action as necessary. Since the FAA issued AD 89-24-06 R1, Transport Canada, the aviation authority for Canada, revised its mandatory continuing airworthiness information (MCAI) to correct this unsafe condition on these products. This AD retains the actions required by AD 89-24-06 R1, extends the compliance time intervals for the repetitive inspections, adds Model DHC-6-400 airplanes to the applicability, and adds a fluorescent penetrant inspection requirement. The FAA is issuing this AD to address the unsafe condition on these products.

Airworthiness Directives; Viking Air Limited (Type Certificate Previously Held by Bombardier, Inc. and de Havilland, Inc.) Airplanes

The FAA is adopting a new airworthiness directive (AD) for certain Viking Air Limited (type certificate previously held by Bombardier, Inc. and de Havilland, Inc.) Model DHC-6-1, DHC-6-100, DHC- 6-200, DHC-6-300, and DHC-6-400 airplanes. This AD was prompted by mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI identifies the unsafe condition as loose quadrants on the rudder pedal torque tube and signs of loose rivets or rivet joint wear due to inadequate manufacturing tolerances. This AD requires inspecting the rudder pedal torque tube quadrant for looseness and taking corrective action as necessary. The FAA is issuing this AD to address the unsafe condition on these products.

Airworthiness Directives; Viking Air Limited (Type Certificate Previously Held by Bombardier Inc. and de Havilland, Inc.) Airplanes

The FAA is adopting a new airworthiness directive (AD) for certain Viking Air Limited (type certificate previously held by Bombardier Inc. and de Havilland, Inc.) Model DHC-6-400 airplanes. This AD was prompted by mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as corrosion of the fuel system components located in the fuel gallery due to inadequate corrosion protection. This AD requires repetitively inspecting the fuel gallery for corrosion, rectifying any deficiencies, and accomplishing modifications to the fuel gallery system. The FAA is issuing this AD to address the unsafe condition on these products.

Airworthiness Directives; Viking Air Limited (Type Certificate Previously Held by Bombardier, Inc. and de Havilland, Inc.) Airplanes

The FAA is superseding Airworthiness Directive (AD) 80-13-10, AD 80-13-12 R1, and AD 2008-03-01, which applied to certain de Havilland (type certificate now held by Viking Air Limited) Model DHC- 6-1, DHC-6-100, DHC-6-200, and DHC-6-300 airplanes. AD 80-13-10 required repetitively inspecting the main landing gear (MLG) legs for cracks and corrosion. AD 80-13-12 R1 required repetitively inspecting each engine nacelle lower longeron for cracks and buckling. AD 2008-03- 01 required incorporating inspections, modifications, and life limits of certain structural components into the aircraft maintenance program. Since the FAA issued those ADs, new and more restrictive airworthiness limitations have been issued for certain structural components. This AD requires incorporating into maintenance records new or revised life limits, modification limits, and inspection or overhaul intervals. The FAA is issuing this AD to address the unsafe condition on these products.

Airworthiness Directives; Viking Air Limited (Type Certificate Previously Held by Bombardier Inc.; de Havilland, Inc.) Airplanes

The FAA is adopting a new airworthiness directive (AD) for all Viking Air Limited (Viking) Models DHC-6-1, DHC-6-100, DHC-6-200, DHC- 6-300, and DHC-6-400 airplanes. This AD results from mandatory continuing airworthiness information (MCAI) issued by the aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as occurrences of excessive wear of elevator cables at pulley location station (STA) 270.3. The FAA is issuing this AD to require actions to address the unsafe condition on these products.

Airworthiness Directives; Viking Air Limited Airplanes

We are adopting a new airworthiness directive (AD) for Viking Air Limited Models DHC-6-1, DHC-6-100, DHC-6-200, DHC-6-300, and DHC-6- 400 airplanes. This AD results from mandatory continuing airworthiness information (MCAI) issued by an aviation authority of another country to identify and address an unsafe condition on an aviation product. The MCAI describes the unsafe condition as aileron cable wear; fouling at the wing root rib, fuselage skin, and wing root rib fairlead; and/or fraying of the cable from the root rib fairlead. We are issuing this AD to require actions to address the unsafe condition on these products.

Airworthiness Directives; Viking Air Limited Model DHC-6-1, DHC- 6-100, DHC-6-200, and DHC-6-300 Airplanes

We are superseding an existing airworthiness directive (AD) for the products listed above. This AD results from mandatory continuing airworthiness information (MCAI) issued by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as:

Airworthiness Directives; Viking Air Limited DHC-6 Series Airplanes

We are adopting a new airworthiness directive (AD) for the products listed above. This AD results from mandatory continuing airworthiness information (MCAI) issued by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as:

Airworthiness Directives; Viking Air Limited Models DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-300 Airplanes

We are adopting a new airworthiness directive (AD) for the products listed above. This AD results from mandatory continuing airworthiness information (MCAI) issued by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as:

Airworthiness Directives; Viking Air Limited Models DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-300 Airplanes

We are adopting a new airworthiness directive (AD) for the products listed above. This AD results from mandatory continuing airworthiness information (MCAI) issued by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as:

Airworthiness Directives; Bombardier Inc. Models DHC-6-1, DHC-6- 100, DHC-6-200, and DHC-6-300 Airplanes

This document adopts a new airworthiness directive (AD) that applies to all Bombardier Inc. (Bombardier) Models DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-300 airplanes that are equipped with pneumatic deicing boots. This AD requires revising the Airplane Flight Manual (AFM) to include requirements for activation of the airframe pneumatic deicing boots. This AD is the result of reports of in-flight incidents and an accident that occurred in icing conditions where the airframe pneumatic deicing boots were not activated. The actions specified by this AD are intended to assure that flightcrews activate the pneumatic wing and tail deicing boots at the first signs of ice accumulation. This action will prevent reduced controllability of the aircraft due to adverse aerodynamic effects of ice adhering to the airplane prior to the first deicing cycle.

Airworthiness Directives; de Havilland Inc. Models DHC-6-1, DHC- 6-100, DHC-6-200, and DHC-6-300 Airplanes

This amendment adopts a new airworthiness directive (AD) that applies to all de Havilland Inc. Models DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-300 airplanes. This AD requires amending the Limitations Section of the airplane flight manual (AFM) to prohibit the positioning of the power levers aft of the flight idle stop while the airplane is in flight. The AFM amendment includes a statement of consequences if the limitation is not followed. This AD is a result of numerous incidents and five documented accidents involving airplanes equipped with turboprop engines where the propeller beta was improperly utilized during flight. None of the incidents or accidents involved de Havilland Inc. Models DHC-6-1, DHC-6-100, DHC-6- 200, and DHC-6-300 airplanes. The actions specified by this AD are intended to prevent loss of airplane control or engine overspeed with consequent loss of engine power caused by the power levers being positioned aft of the flight idle stop while the airplane is in flight.

Airworthiness Directives; de Havilland DHC-6 Series Airplanes

This amendment supersedes Airworthiness Directive (AD) 78-26- 02, which currently requires repetitively inspecting the fuselage side frame flanges at Fuselage Station (FS) 218.125 and FS 219.525 for cracks on certain de Havilland DHC-6 series airplanes, and repairing or replacing any cracked part. The Federal Aviation Administration's policy on aging commuter-class aircraft is to eliminate or, in certain instances, reduce the number of certain repetitive short-interval inspections when improved parts or modifications are available. This AD requires modifying the fuselage side frames at the referenced FS areas as terminating action for the repetitive inspections that are currently required by AD 78-26-02. The actions specified in this AD are intended to prevent failure of the fuselage because of cracks in the fuselage side frames, which, if not detected and corrected, could result in loss of control of the airplane.

Airworthiness Directives; De Havilland DHC-6 Series Airplanes

This amendment adopts a new airworthiness directive (AD) that applies to de Havilland DHC-6 series airplanes that do not have a certain wing strut modification (Modification 6/1581) incorporated. This action requires inspecting the wing struts for cracks or damage (chafing, etc.), replacing wing struts that are found damaged beyond certain limits or are found cracked, and incorporating Modification No. 6/1581 to prevent future chafing damage. This AD results from several reports of wing strut damage caused by the upper fairing rubbing against the wing strut. The actions specified by this AD are intended to prevent failure of the wing struts, which could result in loss of control of the airplane.

Airworthiness Directives; de Havilland, Inc. DHC-6 Series Airplanes

This amendment adopts a new airworthiness directive (AD) that applies to de Havilland DHC-6 series airplanes. This action requires revising the Airplane Flight Manual (AFM) to provide the flight crew with recognition cues for, and procedures for exiting from, severe icing conditions, and to limit or prohibit the use of various flight control devices. This amendment is prompted by results of a review of the requirements for certification of the airplane in icing conditions, new information on the icing environment, and icing data provided currently to the flight crews. The actions specified by this AD are intended to minimize the potential hazards associated with operating the airplane in freezing rain or freezing drizzle conditions by providing more clearly defined procedures and limitations associated with such conditions.

Airworthiness Directives; de Havilland DHC-6 Series Airplanes

This amendment supersedes Airworthiness Directive (AD) 83-26- 05 and AD 86-15-08, which currently require repetitively inspecting the horizontal stabilizer attachment fittings for cracks or looseness on certain de Havilland DHC-6 series airplanes, and, if a cracked or loose part is found, modifying the horizontal stabilizer. This action retains the repetitive inspection requirement of the existing AD's, requires incorporating an improved modification for airplanes with a certain modification design as terminating action for the repetitive inspections, and making these inspection-terminating modifications optional for other affected airplanes. Reports of loose horizontal stabilizer attachment fittings on airplanes incorporating the inspection-terminating modifications required by AD 83-26-05 prompted this action. The actions specified by this AD are intended to prevent separation of the horizontal stabilizer from the airplane caused by a cracked attachment fitting, and subsequent loss of control of the airplane.

Airworthiness Directives; de Havilland DHC-6 Series Airplanes

This amendment supersedes Airworthiness Directive (AD) 83-18- 03, which currently requires repetitively inspecting the tailplane outboard hinge assembly on certain de Havilland DHC-6 series airplanes, and replacing any cracked tailplane outboard hinge assembly. The Federal Aviation Administration's policy on aging commuter-class aircraft is to eliminate or, in certain instances, reduce the number of certain repetitive short-interval inspections when improved parts or modifications are available. This action requires eventually modifying the tailplane outboard hinge arm and tailplane hinge plate with parts of improved design (Modification No. 6/1799) as terminating action for the currently required repetitive inspections. The actions specified by this AD are intended to prevent tailplane failure caused by cracks in either outboard hinge arm or the hinge plate, which, if not detected and corrected, could result in loss of control of the airplane.

Airworthiness Directives; de Havilland DHC-6 Series Airplanes

This amendment supersedes Airworthiness Directive (AD) 73-05- 03, which currently requires repetitively inspecting the rear spar cap for cracks on certain de Havilland DHC-6 series airplanes, and replacing any cracked rear spar cap. The Federal Aviation Administration's policy on aging commuter-class aircraft is to eliminate or, in certain instances, reduce the number of certain repetitive short-interval inspections when improved parts or modifications are available. This action requires modifying the wing rear spar support (Modification No. 6/1301) as terminating action for the currently required repetitive inspections. The actions specified by this AD are intended to prevent cracking of the top flange of the wing spar attachment caps, which, if not detected and corrected, could result in loss of control of the airplane.

Airworthiness Directives; de Havilland DHC-6 Series Airplanes

This amendment supersedes Airworthiness Directive (AD) 81-10- 11, which currently requires repetitively inspecting the elevator root ribs for cracks on de Havilland DHC-6 series airplanes, and replacing any cracked part. The Federal Aviation Administration's policy on aging commuter-class aircraft is to eliminate, or, in certain instances, reduce the number of certain repetitive short-interval inspections when improved parts or modifications are available. This action requires modifying the elevator root rib as terminating action for the repetitive inspections currently required by AD 81-10-11. The actions specified by this AD are intended to prevent failure of the elevator root rib, which could result in loss of control of the airplane.